Potassium is important for plant growth and crop yield. However, the effects of potassium (K+) deficiency on silage maize biomass yield and how maize shoot feedback mechanisms of K+ deficiency regulate whole plant growth remains largely unknown. Here, the study aims to explore the maize growth, transcriptional and metabolic responses of shoots to long-term potassium deficiency. Under the K+ insufficiency condition, the biomass yield of silage maize decreased. The transcriptome data showed that there were 922 and 1,107 differential expression genes in DH605 and Z58, respectively. In the two varieties, 390 differently expressed overlapping genes were similarly regulated. These genes were considered the fundamental responses to K+ deficiency in maize shoots. Many stress-induced genes are involved in transport, primary and secondary metabolism, regulation, and other processes, which are involved in K+ acquisition and homeostasis. Metabolic profiles indicated that most amino acids, phenolic acids, organic acids, and alkaloids were accumulated in shoots under K+ deficiency conditions and part of the sugars and sugar alcohols also increased. It revealed that putrescine and putrescine derivatives were specifically accumulated under the K+ deficiency condition, which may play a role in the feedback regulation of shoot growth. These results confirmed the importance of K+ on silage maize production and provided a deeper insight into the responses to K+ deficiency in maize shoots.

Cuticular waxes are mixtures of hydrophobic compounds covering land plant surfaces and play key roles in plant resistance to abiotic and biotic stresses. However, it is still not clear whether the epicuticular wax could protect the plants from infection by anthracnose, one of the most important plant diseases worldwide, which seriously infects sorghum and causes great yield loss. In this study, Sorghum bicolor L., an important C4 crop with high wax coverage, was selected to analyze the relationship between epicuticular wax (EW) and anthracnose resistance. In vitro analysis indicated that the sorghum leaf wax significantly inhibited the anthracnose mycelium growth of anthracnose on potato dextrose agar (PDA) medium, with the plaque diameter smaller than that grown on medium without wax. Then, the EWs were removed from the intact leaf with gum acacia, followed by the inoculation of Colletotrichum sublineola. The results indicated that the disease lesion was remarkably aggravated on leaves without EW, which showed decreased net photosynthetic rate and increased intercellular CO2 concentrations and malonaldehyde content three days after inoculation. Transcriptome analysis further indicated that 1546 and 2843 differentially expressed genes (DEGs) were regulated by C. sublineola infection in plants with and without EW, respectively. Among the DEG encoded proteins and enriched pathways regulated by anthracnose infection, the cascade of the mitogen-activated protein kinases (MAPK) signaling pathway, ABC transporters, sulfur metabolism, benzoxazinoid biosynthesis, and photosynthesis were mainly regulated in plants without EW. Overall, the EW increases plant resistance to C. sublineola by affecting physiological and transcriptome responses through sorghum epicuticular wax, improving our understanding of its roles in defending plants from fungi and ultimately benefiting sorghum resistance breeding.

AimsPotassium is important for plant growth and crop yield. However, the effects of potassium (K+) deficiency on silage maize biomass yield and how maize shoot feedback mechanisms of K+ deficiency regulating whole plant growth remains largely unknown. Here, the study aims to explore the maize growth and transcriptional and metabolic responses of shoots to long-term potassium deficiency.MethodsThe growth of silage maize and its biomass were analyzed with K+ treatment in field and hydroponic experiments. Furthermore, transcriptional and metabolic profiles of shoots were investigated for their effects on maize development under K+ deficiency condition. ResultsUnder K+ insufficiency condition, the biomass yield of silage maize decreased by 14%-17% in two-year field trials. The transcriptome data showed that there were 390 differently expressed genes overlapping and similarly regulated in the two varieties and they were considered as the fundamental responses to K+ deficiency in maize shoots, with many stress-induced genes involved in transport, primary and secondary metabolism, regulation, and other processes involved in K+ acquisition and homeostasis. Metabolic profiles indicated that most amino acids, phenolic acids, organic acids, and alkaloids were accumulated in shoots under K+ deficiency condition and part of the sugars and sugar alcohols also increased. ConclusionOur results suggested putrescine and putrescine derivatives were specifically accumulated under K+ deficiency condition, which may play a role in feedback regulation of shoot growth. These results confirmed the importance of K+ on silage maize production and provided a deeper insight into the responses to K+ deficiency in maize shoots.